It appears Chat is down:
From the screenshot, we can see that
chat.crypto.stackexchange.com was requested and indeed, requesting this address reproducibly gives the shown error (it also gives a certificate domain missmatch error for me). Whether this a bug or not, I don't know (also I'm mildly surprised that this DNS record even exists).
Now, what you are actually looking for is
chat.stackexchange.com as the server hosting does so for all rooms for all stackexchange sites (excluding stackoverflow). If the problem persists with the correct URL, please comment, so we can escalate the issue if neccessary.
As this issue also affects other site's subdomains I have posted it to Meta.SE for further tracking and handling, though don't expect a "fix" soon as this is just a site that couldn't be generated and doesn't impact anything else.